Option in the Portfolio and FX Portfolio – Virtual FX Position sections of the TWS Account Window that lets you specify the positions that you would prefer IBKR to liquidate last in the event of a margin deficit.

Last liquidation “Yes” or “No” tag. If set to “Yes” this position will be put at the end of the queue to liquidate last in the case of margin requirements. To set, use the right-click menu on the desired position.

While IBKR will attempt on a best efforts basis to honor those requests, account positions and market conditions may make doing so impractical. IBKR therefore reserves the right to liquidate in the sequence deemed most optimal.